<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>验证</title>
  <script>
    function changeCode(){
      let img = document.getElementById("codeImg");
      img.src="/checkCode?"+Math.random();
    }
  </script>
</head>
<body>
  验证码：<img src="/checkCode" alt="验证码" id="codeImg"> <a href="javascript:changeCode()">看不清，楚换一张</a><br>
  请输入验证码：<input type="text" name="code">
</body>
</html>